1. Technical Field
The present invention relates to a data transceiving technology in wireless local area network, and more particularly, to a method for data transceiving method based on data multiplexing and apparatus for the same.
2. Related Art
With the development of information communication technologies, a variety of wireless communication technologies have been developed. Among these technologies, wireless local area network (WLAN) is a technology that Internet access is possible in a wireless way in homes, business or specific service providing areas, using portable terminal such as personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), or the like, based on wireless frequency technologies.
WLAN technologies is created and standardized by the IEEE 802.11 Working Group under IEEE 802 Standard Committee. IEEE 802.11a provides a maximum PHY data rate of 54 Mbps using a 5 GHz unlicensed band. IEEE 802.11b provides a maximum PHY data rate of 11 Mbps by applying a direct sequence spread spectrum (DSSS) modulation at 2.4 GHz. IEEE 802.11g provides a maximum PHY data rate of 54 Mbps by applying orthogonal frequency division multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a PHY data rate of 300 Mbps using two spatial streams and bandwidth of 40 MHz, and provides a PHY data rate of 600 Mbps using four spatial streams and bandwidth of 40 MHz.
As such WLAN technology becomes more prevalent and its applications become more diverse, there is increasing demand for new WLAN technology that can support a higher throughput than IEEE 802.11n. Very high throughput (VHT) WLAN technology, that is one of the IEEE 802.11 WLAN technologies, is proposed to support a data rate of 1 Gbps and higher. IEEE 802.11ac has been developed as a standard for providing VHT in the 5 GHz band, and IEEE 802.11ad has been developed as a standard for providing VHT in the 60 GHz band.
In addition to the above-described standards, various standards on WLAN technologies have been developed, and are being developed. As representative recent technologies, a WLAN technology according to IEEE 802.11af standard is a technology which has been developed for WLAN operation in TV white space bands, and a WLAN technology according to IEEE 802.11ah standard is a technology which has been developed for supporting a great number of stations operating with low power in sub 1 GHz band, and a WLAN technology according to IEEE 802.11ai standard is a technology which has been developed for supporting fast initial link setup (FILS) in WLAN systems. Also, IEEE 802.11ax standard is being developed for enhancing frequency efficiency of dense environments in which numerous access points and stations exist.
In the system based on such the WLAN technologies, an access point (or, a station) may generate an aggregated Medium Access Control (MAC) protocol data unit (A-MPDU) by aggregating a plurality of MPDUs which belong to the same access category (AC) and have the same destination, and transmit the generated A-MPDU.
On the other hand, if multi-user multiple-input multiple-output (MU-MIMO) transmission is used, an access point may transmit a plurality of MPDUs through a single frame even when the plurality of MPDUs belong to different access categories and have different destinations. However, such the transmission is permitted only for downlink MU-MIMO transmission. In addition, in order to support the downlink MU-MIMO transmission, a procedure in which an access point transmits null data packets (NDP) to stations participating the MU-MIMO transmission, a procedure in which the stations which received the NDP perform channel estimation based on the NDP and sequentially report results of the channel estimation to the access point, and a procedure in which the access point controls interferences between the stations and performs the MU-MIMO transmission based on the results of channel estimation are necessary.
In the downlink MU-MIMO transmission, if a large amount of data is to be transmitted, an overhead caused by the procedure for obtaining the results of channel estimation is relatively low. However, if a small amount of data (i.e. small packet) is to be transmitted, the overhead caused by the procedure for obtaining the results of channel estimation becomes relatively high so that efficiency of resources used for supporting the MU-MIMO transmission becomes lower. Also, a proportion of small packets having a size of less than 128 bytes occupies almost 30% of whole packets in a WLAN system, and overhead caused by preambles such as short training field (STF), long training field (LTF), etc. is considerably high in transmission of the small packets.